1. Field of the Invention
The present invention relates to a production process for a carbonized product applicable to a raw material for a carbon material used as a storage battery such as an electric double layer capacitor electrode material and a lithium secondary battery negative electrode material and a raw material for a graphite material used in the high technology fields of semiconductors, atomic power, nuclear fusion, space air navigation and the like, a carbonized product obtained by the above production process, activated carbon for an electric double layer capacitor electrode obtained by subjecting the above carbonized product to activation treatment and a carbon material for a lithium secondary battery negative electrode obtained by subjecting the above carbonized product to graphitization treatment.
2. Description of the Related Art
In the past, when producing granular and powder-form carbonized products from heavy oil, coal tar and petroleum pitch, block-form and small lump-form initial heat-treated products were produced, and they were molded or crushed after carbonized. For example, when using pitches as a raw material, usually carried out was a process in which the raw material was subjected to heat treatment in a muffle furnace or a controlled atmosphere furnace to produce an undissolved and unmolten initial heat-treated product and in which it was molded, crushed or classified after carbonized. However, such process had the difficulties that steps were complicated and that productivity was low, and industrialization thereof was difficult.
Further, synthetic pitches obtained by polymerizing polyaromatic hydrocarbons such as naphthalene and methylnaphthalene under the presence of hydrogen fluoride and boron trifluoride which are ultra strong acid catalysts had the characteristic that they were molten and foamed to a volume of several ten times based on the raw material if carbonized as they were. Accordingly, a process in which they are carbonized as they are had the defect that industrialization thereof was difficult because of a notably low volume efficiency.
Disclosed is a process in which in order to inhibit melting and foaming in a carbonization step, a reactor is charged in advance with a granular or powder-form carbonized product and in which a raw material pitch is fed under stirring by means of a stirring blade and a double shaft rotator and subjected to heat treatment (refer to, for example, Japanese Patent Application Laid-Open No. 286181/1995). In the above process, however, lumps were liable to be produced because a carbonized product having a low density was used, and a complicated stirring mechanism was required in order to allow the content to satisfactorily move. Accordingly, it had the defect that an expensive apparatus was required.